Process and apparatus for the introduction of gas into a discharge opening of a metallurgical container containing molten metal

ABSTRACT

For the procedure a gas, heated to at least 1000 degrees Celsius, preferably even beyond the liquid temperature of the melt, is blown into the discharge opening (26). In this manner freezing problems and deposits in the discharge opening can be largely prevented. The pouring sleeve (20) according to the invention has a gas supply line (21), leading into a gas permeable insert (23) surrounding the opening (26), which is led for a certain length along the upper range of the sleeve (20) which is in contact with the melt, for the purpose of heating the gas.

The invention concerns a procedure for the introduction of gas into adischarge opening of a matallurgical container in order to prevent orreduce deposits or freezing in the discharge opening, as well as adischarge sleeve for executing the procedure.

During the pouring particularly of metal melts from steel pouring ladlesor spreaders, particularly aluminum killed steel has a tendency to formalumina deposits in the discharge opening, which lead to obstructionsand early discontinuation of pouring. According to DE-PS No. 35 06 426it has been known to fight such deposits with the introduction of gas.The gas there is blown in at room temperature with a constant gas streamor also in a pulse like manner.

In another procedure of the generic type (DE-PS No. 28 36 409 ), inwhich a slide lock is arranged at the discharge opening of thecontainer, a flush gas is blown into the discharge opening through theslide plate with closed lock in order to prevent the freezing of themelt in the opening.

In practice it has been possible to deal with this problem with more orless success with the use of these known procedures.

Starting from this, the current invention is based on the problem toimprove the gas introduction in such a manner that the cited deposits orfreezing in the discharge opening can be prevented in a simple mannerfor the duration of the required pouring time.

According to the invention this problem has been solved due to the factthat the gas is heated before entering the discharge opening to at least1000 degrees Celsius, preferably even beyond the liquid temperature ofthe metal melt. In this manner the pouring times or temporary closingtimes can be extended practically as long as desired without any pouringdisruptions.

Due to the blowing in of heated gas, the melt in the discharge openingduring the pouring does not undergo any appreciable cooling into thetemperature range suitable for alumina precipitation or even a clingingto the opening wall due to gelling of the melt.

With the use of a slide lock at the discharge of the container it ispossible to completely prevent, in a locked position of the closure, afreezing of the melt in the discharge opening by blowing in heated gasthrough a locking plate into the discharge opening, provided the gastemperature is above the liquid temperature of the melt.

In the procedure according to the invention the preferred gas to us isan inert gas, such as argon to a gas-solid matter mixture.

The gas can be heated by means of an external heating device or by adischarge sleeve according to the invention in which the cold gas is ledfor a certain distance through a gas supply line in the upper area ofthe sleeve which is in contact with the metal melt and is then blowninto the melt through a gas permeable insert surrounding the dischargeopening. In this manner the gas is heated without problem to beyond themelting point of the melt and a freezing as well as a possible aluminadeposit at the opening wall can be prevented for the whole requiredpouring time.

Advantages of further variations of the discharge sleeves according tothe invention are explained in the following description.

It is certainly also possible that heated gas can be blown in a suitablemanner into the extended discharge opening, formed by a pouring tube, orthrough a locking plate.

Embodiments of the invention are explained below based on the drawing.Shown is:

FIG. 1 A procedure according to the invention based on a pouring sleevearranged in the discharge opening of the container and shown inlengthwise section,

FIG. 2 a procedure according to the invention, applied with a slidelock, in locked position, arranged on the discharge,

FIG. 3 variation of a pouring sleeve in lengthwise section,

FIG. 4 cross section of the pouring sleeve according to FIG. 3 on theline IV--IV,

FIG. 5 further variation of a pouring sleeve in lengthwise section,

FIG. 6 cross section of the pouring sleeve according to FIG. 5 on theline VI--VI,

FIG. 7 fourth variation of a pouring sleeve in lengthwise section and

FIG. 8 topview of the sleeve according to FIG. 7.

Shown in FIG. 1 is the discharge area of a container 10, containing ametal melt, in which the discharge is formed by a fireproof dischargesleeve 20, to which schematically shown fireproof locking plates 15 and17 of an actually known slide lock are connected. The partially showncontainer 10 can be, for example, a steel pouring ladle or a spreaderand essentially consists of a steel casing 14 and a fireproof insidelining 12 into which the discharge sleeve 20 is embedded. By means ofthe lower locking plate 17, pressed against the upper locking plate 15,it is possible to pour the amount of melt in a regulated manner byshifting said plate. In the shown position, in which the openings of thelocking plates 15 and 17 are the same as the discharge opening 26, thelock is fully opened.

The pouring sleeve 20 of fireproof material has an annular gas permeableinsert 23 which surrounds the discharge opening 26 and is surrounded atits circumference by a metal capsule 25, whereby an annular gap 27 isprovided in between which permits an even distribution of the gas comingfrom the gas supply line 21. For the heating of the gas to be blown intothe discharge opening 26 according to the invention, the gas supply line21 is led into the upper range of the pouring sleeve 20, there led in acoil-like manner around the discharge opening 26 and then led heatedthrough the insert 23 into the melt to be poured. The gas supply line21', constructed in a coil-like manner in the upper range of the pouringsleeve 20, is embedded into a fireproof extension 22, consisting of wellheat conducting material, e.g., electro-graphite which is glued to thesleeve. During the time the blown in gas remains in this extension 22which is in contact with the metal melt and very rapidly assumes thetemperature of the melt, the gas is also very rapidly heated to atemperature which is almost the same as that of the melt. For thispurpose the gas supply line 21 consists of a highly heat resistant steelor a fireproof ceramic tube.

In particular for preventing the freezing in the discharge opening 26with closed slide lock, the gas heated in the pouring sleeve 20 is ledthrough an additional line 21", shown only by a dot-dash line in FIG. 1,to a gas permeable insert 16 which is embedded in the upper lockingplate 15 and surrounds the discharge opening 26 and from there blowninto the discharge opening 26. In this manner it is possible tosuccessfully prevent a freezing of the melt in this opening, forexample, during a temporary closing of the lock for the purpose ofexchanging the pouring tube or other reasons.

According to FIG. 2 the heated gas is introduced, also for a preventionof freezing with a closed slide lock 33, only shown schematically,through a gas permeable stopper 35 which is mounted in a sliding plate34 and gets under the discharge opening 26 in a locked position. Forthis purpose the gas is led from a not shown gas source G through aheating device 30 and a heat resistant gas supply line 31 into thestoper 35, whereby the latter has borings for an effective blowing in.In a corresponding manner, the inserts surrounding the discharge openingcan also contain such borings.

With an opened lock 33 the procedure according to the invention can,depending on the application, also be used with a pouring tube 36,connected to the lock 33, the discharge opening 37 of which has aninsert 38. The gas is heated in the heating device 30 and led through aheat resistant line 32 into this insert 38 and thus into the dischargeopening. The heating device 30 is also only shown schematically and maybe a known flow heater. The slide lock 33 is arranged on the dischargeof the container 10 and essentially consists of three fireproof plates34, 39 and 41, whereby the upper and the lower plate 39 and 41 arefixed, while the center plate 34 is led in a longitudinally shiftablemanner.

A variation of a pouring sleeve 40 in container 10 according to FIG. 3and FIG. 4 consists of a fireproof body 42 and an in it embedded porousinsert 43. The porous insert 43 again surrounds the discharge opening26. The gas supply G is done through the slit line 44, molded into thesleeve 40, which again is led into the upper sleeve area. The line 44comprises a first and a second annular slit 44' around the dischargeopening 26 and a slit 44", led in an open space 45 surrounding theinsert 43. In this variation too, it is possible to heat the gas to therequired temperature.

FIG. 5 and FIG. 6 show a pouring sleeve 50, embedded in the container 10as another variation of the invention. This sleeve 50 is a fireproofconcrete poured in a sheet metal casing 51. The gas supply G is througha line 52, poured into the sleeve, which is again led in the upper partof the sleeve 50 in a coil-like manner around the discharge opening 26and from there into a porous insert 55 with a sheet metal casing, whichis also molded into the casing. Here too, the remainder time in coils52' and 52" is sufficient for the heating of the gas.

The pouring sleeve 60 shown in FIG. 7 and FIG. 8, consists of a fullyporous fireproof body 61 with a discharge opening 26 and a sheet metalcasing 62 surrounding the body 61. Between the body 61 and the sheetmetal casing 62 an annular space 63 is provided into which the heatedgas is led through a line 64, connected to the gas supply G. The gassupply line 64 has a loop 64' which is in contact with the metal meltoutside and around the sleeve 61 and thus consists of a fireproofceramic tube.

The invention can also very well be applied to non-iron metals, such asaluminum melts where the melting temperature is relatively low and thusthe gas does not have to be heated so high. The described pouringsleeves can also be actually known perforated brick mounted with mortarinto the steel pouring ladles.

What is claimed is:
 1. In a process of introducing gas into a dischargeopening of a metallurgical vessel containing molten metal, theimprovement comprising preventing or reducing the formation in saiddischarge opening of deposits from the molten metal and the freezing ofthe molten metal in said discharge opening by:prior to introducing saidgas into said discharge opening, heating said gas to a temperature of atleast 1000°C.
 2. The improvement claimed in claim 1, comprisingintroducing said gas into said discharge opening with said gas heated toa temperature above the liquidus temperature of the molten metal.
 3. Theimprovement claimed in claim 1, comprising introducing said gas intosaid discharge opening by blowing said gas through a gas permeableinsert surrounding said discharge opening.
 4. The improvement claimed inclaim 3, wherein said insert is positioned within a refractory dischargesleeve defining said discharge opening and fitted within themetallurgical vessel.
 5. The improvement claimed in claim 4, whereinsaid heating comprises passing said gas through a passage at an innerend of said discharge sleeve in contact with the molten metal in themetallurgical vessel.
 6. The improvement claimed in claim 5, whereinsaid passage is located within said inner end of said discharge sleeve.7. The improvement claimed in claim 5, wherein said passage surroundssaid inner end of said discharge sleeve.
 8. The improvement claimed inclaim 6, wherein said insert is positioned within a plate of a slidegate mounted on the metallurgical vessel to selectively open and closesaid discharge opening.
 9. The improvement claimed in claim 8, whereinsaid plate is a stationary plate of said slide gate.
 10. The improvementclaimed in claim 8, wherein said plate is slidable plate of said slidegate.
 11. The improvement claimed in claim 1, comprising heating saidgas by means of a heating device external of the metallurgical vessel.12. The improvement claimed in claim 1, comprising heating said gas bymeans of a heat exchange medium.
 13. The improvement claimed in claim 1,comprising introducing said gas into said discharge opening by blowingsaid gas through a porous discharge sleeve difining said dischargeopening and fitted within the metallurgical vessel.
 14. The improvementclaimed in claim 13, wherein said heating comprises passing said gasthrough a passage positioned outwardly of said discharge sleeve.
 15. Theimprovement claimed in claim 14, wherein a portion of said passage islocated at an inner end of said discharge sleeve in contact with themolten metal in the metallurgical vessel.
 16. The improvement claimed inclaim 1, wherein said gas is an inert gas.
 17. The improvement claimedin claim 1, wherein said gas is a gas-solid mixture.
 18. In a refractorydischarge sleeve to be mounted in a metallurgical vessel to containmolten metal, said discharge sleeve having therethrough a dischargeopening for discharging the molten metal from the vessel, a gaspermeable member surrounding at least a portion of said dischargeopening, and means for supplying gas to said gas permable portion suchthat the gas permeates therethrough and is introduced into saiddischarge opening, the improvement comprising means for preventing orreducing the formation in said discharge opening of deposits from themolten metal and freezing of the molten metal in said discharge opening,said preventing or reducing means comprising:means for, prior tointroduction of the gas into said discharge opening, heating the gas toa temperature of at least 1000°C., said heating means comprising aportion of said supplying means upstream of said gas permeable portionbeing located at an inner end of said discharge sleeve to be in contactwith the molten metal in the metallurgical vessel.
 19. The improvmentclaimed in claim 18, wherein said portion of said supplying means isformed as a coil surrounding said discharge opening.
 20. The improvmentclaimed in claim 18, further comprising a refractory annular extensionmounted on said inner end of said discharge sleeve such that saidannular extension is to be in contact with the molten metal, saidannular extension being formed of a highly heat conductive material, andsaid portion of said supplying means extends through said annularextension.
 21. The improvement claimed in claim 19, wherein saidmaterial of said annular extension is electro-graphite.
 22. Theimprovement claimed in claim 18, wherein said portion of said supplyingmeans comprises a refractory ceramic tube surrounding said inner end ofsaid discharge sleeve and to be contacted by the molten metal.
 23. Theimprovement claimed in claim 18, wherein said portion of said supplyingmeans is embedded in the material of said discharge sleeve.
 24. Theimprovement claimed in claim 18, wherein said portion of said supplyingmeans comprises channels formed in the material of said dischargesleeve.
 25. The improvement claimed in claimed 18, wherein said gaspermeable member comprises an annular gas permeable insert embedded inthe material of said discharge sleeve.
 26. The improvement claimed inclaim 18, wherein said discharge sleeve is entirely formed of porousmaterial forming said gas permeable member, and further comprising ametal casing peripherally surrounding said porous discharge sleeve.